1. Field of the Invention
This invention relates in general to the use of light-sensitive polymeric compositions in the graphic arts to produce photomechanical images and in particular to improvements in the image-forming development of positive-working photoresist films and positive-working lithographic printing plates containing light-sensitive quinone diazides. More specifically, this invention relates to the use of certain developing compositions which provide improved results in the development of the aforesaid photoresist films and printing plates.
2. Description of the Prior Art
An important class of light-sensitive materials that is widely utilized in the graphic arts in the formation of photomechanical images is the class of quinone diazides. These materials enjoy extensive use in such important applications as positive-working photoresist films and positive-working lithographic printing plates. Exposure of the composition to actinic radiation results in a solubility differential between the exposed and unexposed areas such that treatment with an appropriate developer results in removal of the radiation struck areas and retention of the desired image areas on the support. It is believed that such exposure decomposes the diazo structure in the radiation struck areas to form the free carboxylic acid group, thereby rendering the exposed areas soluble in alkaline developer solutions. The developer solutions which are employed for this purpose can be aqueous solutions or organic solutions. Typical examples of alkaline developer solutions utilized heretofore in development of quinone diazide compositions include solutions of sodium hydroxide, ammonium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate or sodium phosphate. Developers containing lower alcohols, ketones, or amines such as the alkyl amines, cycloalkyl amines and alkanolamines, are also well known.
It is known to use quaternary ammonium hydroxide developing agents in developer compositions that are employed in developing light-sensitive quinone diazide compositions. Thus, for example, the use of tetraalkylammonium hydroxides, such as tetramethylammonium hydroxide or tetraethylammonium hydroxide, as developing agents is described in Japanese Patent Publication No. 56226/1976 published May 17, 1976. Use of tetramethylammonium hydroxide as a developing agent is also described in British Pat. No. 1,367,830. Especially useful quaternary ammonium hydroxide developing agents are the quaternary alkanol ammonium hydroxides such as, for example, the methyltriethanolammonium hydroxide of U.S. Pat. No. 4,141,733. As described in this patent, this developing agent is particularly advantageous for use in forming a metal-ion-free developer composition that is especially adapted for forming fine image detail in the utilization of photoresists in the manufacture of integrated circuit devices. Developer compositions containing methyltriethanolammonium hydroxide provide many highly advantageous characteristics such as extended development latitude, increased exposure latitude, improved resist contrast, improved prebake latitude, a low depletion rate and minimal loss of image layer thickness.
While developer compositions containing a quaternary alkanol ammonium hydroxide developing agent are excellent developers for resists of the quinone diazide type, they suffer from a serious problem in that gradual decomposition of the quaternary alkanol ammonium hydroxide compound, with consequent darkening of the composition and changes in its performance as a developer, tends to take place. It is toward the objective of providing a developer composition that is stable, so that its performance does not change significantly with the passage of time, i.e., a developer composition that has a relatively long "shelf-life", that the present invention is directed.